What are Piaget's stages of cognitive development?

Jean Piaget, a Swiss scientist who lived from 1896 to 1980, was something of a jack-of-all-trades when it came to matters of the human mind -- specifically, the minds of children. A precocious child himself, penning his first scientific paper when he was just 11 years old, Piaget would publish more than 60 books and several hundred articles over the course of his long, diverse career [source: Jean Piaget Society].

Perhaps best known for his Theory of Cognitive Development, Piaget and his colleagues developed experiments that illuminated differences in the way children of various ages are able to grasp and process the world around them, as well as how they grow to possess the use of logic and reasoning as they age.

This ties in with a term Piaget coined known as genetic epistemology, the study of how knowledge is acquired and the mechanisms and process that are involved. What he found was that our knowledge and reasoning skills develop in tandem with our biological growth. Young children are not just "dumb adults" as some people like to joke; they actually think very differently from older children.

Piaget's theory is not without its detractors. Later research suggests it's too rigid, at least in its age designations, and that children often develop sooner than Piaget gave them credit for. On the flip side, it appears many people move more slowly through the four stages and some never manage to master the fourth and final stage of development at all, leading to further questions about how heavily biological development features into the equation. Others claim Piaget's theory underestimates the impact culture and gender differences can have on children.

But despite investigations that led to alternative scientific theories, Piaget's theory was a groundbreaking work that heavily influenced the field of childhood development and educational models. So on the next four pages, we'll take a tour through the mind of a child as she grows -- our own little psychological test subject -- according to the changes that would be happening in her mind as if she were developing precisely along Piaget's line of thinking.